Security readout for executives and security teams
Plain-English summary
UPX has a reported memory-safety flaw where a specially crafted Mach-O file can make an affected UPX 4.0.0 development build read past a heap buffer. The public bundle does not state business impact, active exploitation, or a named fixed release.
Executive priority
Prioritize this for teams that use UPX on untrusted Mach-O files. It is not supported as an internet-wide emergency by the provided evidence, but it deserves cleanup in security tooling and build environments.
Technical view
CVE-2020-27800 is a heap-based buffer over-read in UPX get_le32 in bele.h, triggered via a crafted Mach-O file. The listed affected version is upx 4.0.0-git-87b73e5cfdc1+. CWE-119 is assigned. No CVSS score is provided in the source bundle.
Likely exposure
Exposure is most likely where the affected UPX development build processes Mach-O files, especially automated malware analysis, binary inspection, packaging, or unpacking workflows. The sources do not identify broader affected releases or platforms.
Exploitation context
The bundle marks KEV as false and provides no cited evidence of active exploitation. The only described trigger is a crafted Mach-O file processed by affected UPX code.
Researcher notes
Public details are sparse: no CVSS, no patch reference, no exploit status, and no impact statement beyond heap-based over-read. Treat conclusions outside the affected build, code location, and crafted Mach-O vector as unconfirmed unless upstream issue 395 adds evidence.
Mitigation direction
- Inventory UPX versions used in developer, CI, and analysis systems.
- Avoid processing untrusted Mach-O files with the affected development build.
- Check the upstream UPX issue for vendor-confirmed fixed versions or guidance.
- Replace affected UPX builds once a vendor-confirmed safe version is identified.
Validation and detection
- Confirm whether upx 4.0.0-git-87b73e5cfdc1+ exists in your environment.
- Identify workflows where UPX processes Mach-O files.
- Review whether UPX runs with unnecessary privileges in automated tooling.
- Track GitHub issue 395 and CVE records for severity or fix updates.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-119: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2020-27800 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Unknown
- CVSS
- Not scored
- Known Exploited
- No
- Published
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS and timeline data
No CVSS vectors or timeline events were available in the normalized CVE source material.
Source materials
- CVE List V5 sourceCVE List V5
- https://github.com/upx/upx/issues/395CVE reference · x_refsource_MISC
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Improper Restriction of Operations within the Bounds of a Memory Buffer
Improper Restriction of Operations within the Bounds of a Memory Buffer represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.